Manufacture of organic compounds



Patented Feb. 15, 1938 UNITED STATES PATENT OFFICE No Drawing. Originalapplication August 25,

1933, Serial No. 686,737. Divided and this application September 5,1935, Serial No. 39,- 285. In Great Britain September 1, 1932 7 Claims.

This invention relates to the manufacture of ethers of .glycols,glycerol or other polyhydric alcohols, and particularly to themanufacture of ethers containing two molecules of such hydroxy morehydroxy groups, and is a divisional of copending application, S. No.686,737.

According to the present invention ethers of glycols, glycerol or otherpolyhydric alcohols are i produced by subjecting the polyhydrio alcoholstogether with metal oxides, and particularly alkali or alkaline earthmetal oxides, to the action of heat. The process of the invention isprefer-ably carried out in the presence of hydrogen chloride.

It may be remarked that the ethers formed from two molecules of ethyleneglycol or two molecules of glycerol in which all the hydroxyl groupshave furnished ether linkages, dioxane 20 and diglycerol triether,possess very valuable properties, for example as solvents for organicderivatives of cellulose and that these compounds in particular may bemade in a very satisiactory manner by the process of the presentinvention.

The polyhydric alcohols may be employed in chemical combination with themetal oxides, i. e. in the form of alcoholates such as sodium or calciumalcoholates, or may be employed simply in 30 admixture with the metaloxides. In carrying out the process of the invention the startingmaterial is heated, preferably in the presence of hydrogen chloride, toa suitable temperature and the ether formed may then be removed from the1:5 heating zone, for example by distillation through a column, the topof which is maintained at such a temperature that any hydroxy compoundvapor is returned to the reaction zone, while the ether remainsuncondensed.

40 When it is desired to employ the polyhydric alcohols in chemicalcombination in the form of alcoholates preferably alkali or alkalineearth alcoholates are used such as the sodium or calcium alcoholate of,for example, glycerol. By heating such an alcoholate in an atmospherecomprising hydrogen chloride gas the ethers, including diglyceroltriether in the case of a glycerol alcoholate may be produced. Suitabletemperatures are, for example, temperatures above 160 C., and

especially between 180 and 200 C. although higher temperatures may beemployed if desired, e. g. temperatures up to 300 0., particularly inthe case where the starting material contains an excess of glycerine.Advantageously,

the reaction is effected under pressures not subd compounds united byether linkages at two or stantially exceeding atmospheric, while ifdesired lower pressures, for example between and 1 atmosphere, may bevemployed.

Although the use of an atmosphere comprising hydrogen chloride is tobepreferred, in that, 5 inter alia, it enables somewhat lower temperaturesto be employed, the invention is not restricted to such use, and theproduction of the ether may be eiiected by simple heating of thestarting material, preferably in an inert atmo-sphere comprising, forinstance, nitrogen or carbon dioxide or in an atmosphere comprising bothsuch an inert gas and hydrogen chloride.

If desired, other substances having a catalytic or condensing action, e.g. calcium chloride, may be employed, either alone or in associationwith each other and/or with hydrogen chloride.

The alcoholates may very conveniently be heated, whether or not hydrogenchloride or other catalyst be employed, in solution or suspension in orotherwise in presence of an inert liquid of high boiling point, such astetrahydronaphthalene, decahydronaphthalene, diphenyl or the like.Preferably the solution or suspension is thoroughly stirred or otherwiseagitated, and, when hydrogen chloride is employed, intimate contacttherewith may further be promoted by leading the gas into the reactionmixture in the form of very fine bubbles such as may be produced byforcing the gas through a porous plate. If desired the agitation of theliquid may be aided by the passage of other gases or vapors, such asnitrogen or carbon dioxide, therethrough, whether or not hydrogenchloride is employed.

Advantageously the ether produced may be removed from the reaction zonein the form of vapor as fast as it is formed, together with the escapingwater vapor and hydrogen chloride gas, from which it may afterwards beseparated in any convenient way. Condensation of the ether produced maybe effected in presence of a substance capable of forming an azeotropicmixture with the ether, whereby the separation of the latter from theparent hydroxy compound and/or the inert solvent or diluent isfacilitated. If desired, the solvent or diluent itself may be capable ofentraining the ether, yielding a mixture free from the hydroxy compoundfrom which the ether may subsequently be separated in any convenientway. F

To aid in separating from the ether the water formed in the reaction, orany Water initially present, a substance capable of forming anazeotropic mixture with water may be employed. Such substances may beinitially present with the starting material to be subjected to thereaction, or, for instance, they may be added to the vapour mixtureleaving the reaction zone, preferably before any condensation has takenplace. Advantageously they may be present in amount sufficient toproduce an azeotropic mixture with all the water present, thus enablingthe ether to be separated, for example by fractional condensation, in analmost completely anhydrous state.

Alternatively the reaction may be effected under such conditions thatthe ether formed is continually returned to the reaction zone, while thewater vapor, with or without an entraining liquid, is allowed to escape.Such separation may conveniently be effected in a fractionating columncontaining, for example Raschig rings.

As previously indicated instead of employing the polyhydric alcohols incombination in the form of alcoholates they may be employed in admixturewith metal oxides, and preferably alkali metal or alkaline earth metaloxides. For example, a mixture of glycerine and calcium oxide may beheated to a suitable temperature and fresh glycerine run into themixture as the ether distils off. Whether the polyhydric alcohol andmetal oxide are in chemical combination or simply in admixture with eachother the quantity of oxide present may be equal to, less than, or morethan that theoretically necessary to form the salt of the polyhydricalcohol.

Although the use of azeotroping substances for the separation of waterfrom the ethers has been specifically described, such removal may beeffected in any other convenient way, either before or aftercondensation of both the ethers and water or of the ethers alone. Thusthe vapors leaving the reaction zone may be led into or otherwisetreated with a liquid at a temperature between the boiling points ofwater and the ether; preferably such liquid may be substantiallyimmiscible with the ether, thus facilitating the subsequent separationof ether from condensing liquid. Again, the reaction vapors may betreated with a liquid having a solvent action on the ether andsubstantially none on the water, or the ether may be passed over ortreated with water binding substances, preferably af er separation, asby fractional condensation, of the greater part of the Water. Any otherconvenient method may, however, be employed.

Even after separation from the water, the ethers may still containhydrogen chloride, which may be removed in any convenient way. Thus thevapors issuing from the reaction zone, before the separation of thewater, may be passed over or otherwise in contact with a neutralizingagent such as sodium carbonate or calcium hydroxide. If desired,however, neutralization may take place after condensation of the ethersor of both the ethers and water. Preferably, however, the water is firstseparated as described above, together with much of the hydrogenchloride, and the condensed ethers subsequently treated with aneutralizing agent. The ethers may be separated from the chloridesiormedand/or excess of the neutralizing agent in any convenient Way, forexample by centrifuging or by distillation.

Any water present in the products of reaction may be removed in anyconvenient manner, as, for example, by fractional condensation, with orwithout the use of an entraining liquid therefor. If the decompositionof the polyhydric alcohol, as such or in the form of an alcoholate, iseffected under conditions of temperature and pressure such that theether does not distill off continuously, the water may be continuouslyremoved by distillation, if desired, in the form of an azeotropicmixture with any suitable substance.

The ether may be separated from the solvent or diluent, if such isemployed, for example with the aid of an entraining substance, or byfractional distillation, or in any other way.

The following examples illustrate the invention, but are not to beconsidered as limiting it in any way:-

Example 1 A mixture of about equal parts by weight of calcium glycerateand diphenyl is heated slowly in a vessel provided with stirrers and anoutlet connected to a condenser leading to a receiver.

When the diphenyl melts the temperature is rapidly raised to -200 C.whilst stirring and hydrogen chloride is passed into the mixture in theform of small bubbles by means of a distributor immersed in it.

The reaction products are condensed and collected in the receiver,uncondensed hydrogen chloride being returned to the process. Afterneutralization with sodium carbonate, the diglycerol triether producedcan be separated by distillation and/or extraction with solvents.

Example 2 A fluid mixture of calcium glycerate and glycerol is subjectedwhilst stirring to dry distillation at a temperature of 240-280 C. andthe diglycerol triether evolved together with lay-products is condensedand worked up as described in the preceding example,

Although the invention has been described specifically with respect tothe manufacture of dioxane and diglycerol triether, it may also beapplied to any similar or homologous dior poly-ethers. Thus, forexample, erythritol or other polyhydroxy compounds or monoor otherethers thereof containing at least two free hydroxyl groups may beconverted into the corresponding ethers. Moreover, the invention is notconfined to the production of symmetrical ethers; thus, for example, byusing a mixture of glycol and glycerol, or glycol and an a-ether ofglycerol, hydroxy methyl dioxane or ethers thereof may be obtained, orby employing glycol and a B-ether of glycerol, a compound containing a7-membered ring may be obtained. Again, instead of employing onlypolyhydric alcohols such compounds may be employed together with, forexample, formaldehyde, acetaldehyde, acetone or homologues thereof, andthe like, so as to produce products of condensation between theformaldehyde etc. and the polyhydric alcohols as well as the polyhydricalcohol-ethers. By this means mixtures having very valuable solventpowers may be produced.

What I claim and desire to secure by Letters Patent is:-

1. Process for the manufacture of a cyclic ether, which comprisessubjecting to the action of heat a polyhydric alcohol in admixture withan oxide of a metal selected from the group consisting of alkali metalsand alkaline earth metals, the metal radicle and the alcohol radiclebeing present in substantially the proportions which react to form ametal alcoholate, passing gaseous hydrogen chloride into the reactionmixture while the said reaction mixture is being heated, and removingthe cyclic other as it is formed.

2. Process for the manufacture of a cyclic ether, which comprisessubjecting to the action of heat at a temperature of at least 160 C.glycerol together with an oxide of a metal selected from the groupconsisting of alkali metals and alkaline earth metals, the metal radicleand the alcohol radicle being present in substantially the proportionswhich react to form the metal alcoholate in which all the hydrogen atomsattached to the hydroxyl groups of the polyhydric alcohols have beensubstituted by metal atoms, passing gaseous hydrogen chloride into thereaction mixture while the said reaction mixture is being heated, andcontinuously removing the cyclic ether as it is formed.

3. Process for the manufacture of a cyclic ether, which comprisessubjecting to the action of heat at a temperature of at least 160 C. aglycol together with an oxide of a metal selected from the groupconsisting of alkali metals and alkaline earth metals, the metal radicleand the alcohol radicle being present in substantially the proportionswhich react to form the metal alcoholate in which all the hydrogen atomsattached to the hydroxyl groups of the polyhydric alcohols have beensubstituted by metal atoms, passing gaseous hydrogen chloride into thereaction mixture while the said reaction mixture is being heated, andcontinuously removing the cyclic ether as it is formed.

4. Process for the manufacture of a cyclic ether, which comprisessubjecting to the action of heat at temperatures of 160 to 300 C. aglycol together with an oxide of a metal selected from the groupconsisting of alkali metals and alkaline earth metals, the metal radicleand the alcohol radicle being present in substantially the proportionswhich react to form the metal alcoholate in which all the hydrogen atomsattached to the hydroxyl groups of the polyhydric alcohols have beensubstituted by metal atoms, passing gaseous hydrogen chloride into thereaction mixture while the said reaction mixture is being heated, andcontinuously removing the cyclic ether as it is formed.

5. Process for the manufacture of a cyclic ether,

which comprises subjecting to the action of heat at temperatures of 160to 300 C. glycerol together with an oxide of a metal selected from thegroup consisting of alkali metals and alkaline earth metals, the metalradicle and the alcohol radicle being present in substantially theproportions which react to form the metal alcoholate in which all thehydrogen atoms attached to the hydroxyl groups of the polyhydricalcohols have been substituted by metal atoms, passing gaseous hydrogenchloride into the reaction mixture while the said reaction mixture isbeing heated, and continuously removing the cyclic ether as it isformed.

6. Process for the manufacture of diglycerol triether, which comprisessubjecting to the action of heat glycerol together with an oxide of ametal selected from the group consisting of alkali metals and alkalineearth metals, the metal radicle and the alcohol radicle being present insubstantially the proportions which react to form the metal alcoholatein which all the hydrogen atoms attached to the hydroxyl groups of thepolyhydric alcohols have been substituted by metal atoms, passinggaseous hydrogen chloride into the reaction mixture while the saidreaction mixture is being heated, and continuously removing the glyceroltriether as itis formed.

7. Process for the manufacture of dioxane, which comprises subjecting tothe action of heat ethylene glycol together with an oxide of a metalselected from the group consisting of alkali metals and alkaline earthmetals, the metal radicle and the alcohol radicle being present insubstantially the proportions which react to form the metal alcoholatein which all the hydrogen atoms attached to the hydroxyl groups of thepolyhydric alcohols have been substituted by metal atoms, passinggaseous hydrogen chloride into the reaction mixture while the saidreaction mixture is being heated, and continuously removing the dioxaneas it is formed.

HENRY DREYFUS.

